Don't Look Down
Skyscraper Project Teams Sidestep Risks to Reach Dizzying New Heights
BY SARAH FISTER GALE
Skyline over Shanghai, China
Jeddah Tower, under construction in Saudi Arabia
PHOTO COURTESY OF SCHWING
In a world where bigger is always better, skyscraper projects are all the rage. In 2016, a record 128 skyscraper projects were completed around the world, with up to 150 more scheduled for 2017, according to the Council on Tall Buildings and Urban Habitat.
And the world's tallest building, the 828-meter (2,717-foot) Burj Khalifa in Dubai, United Arab Emirates (UAE), will soon be overshadowed by the Jeddah Tower in Saudi Arabia—the first skyscraper to reach 1 kilometer (3,281 feet)—when it's completed in 2022. But the extremes don't end there. The proposed Sky Mile Tower in Tokyo, Japan would dwarf both buildings with its 5,577-foot (1,700- meter) design, while another company dreams of building a U-shaped skyscraper in New York, New York, USA that—from end to end—would stretch 4,000 feet (1,219 meters).
“There is no limit,” says Jerry Bianco, senior vice president and operations director for Lendlease in New York, New York, USA, where he has been building skyscrapers for 16 years. He has watched projects get taller, with developers often now negotiating to acquire “air space” so they can cantilever the new building over neighboring buildings to get more square footage out of limited urban footprints.
But as these projects pierce the clouds, designers and project teams face a host of new risks, from safely moving hundreds of workers up and down the structure every day to trucking thousands of pounds of materials into tight job sites—all without annoying neighbors or clogging narrow streets in crowded urban areas.
“There are a lot of restrictions and a lot of risks that all need to be carefully planned and managed,” Mr. Bianco says. “On skyscraper projects we are focused on the safety of personnel and the speed of moving them and materials.”
The quest to go higher is forcing designers—and project managers—to get creative with planning and problem-solving. “It's a constant logistics puzzle,” says Patrick Murray, vice president and construction executive, Turner Construction Co., New York, New York, USA.
Project managers must work with designers, engineers and dozens of suppliers and contractors to build these metal mountains as quickly as possible. And if any stakeholders fail to deliver their piece of the project, from material shipments to on-site labor, it can have a cascading impact on the entire plan.
“You have to start planning years ahead to identify and address all of the risks you will face,” Mr. Murray says. “That way all contractors know the plan upfront and can factor it into their costs and schedule.”
Once contracts are awarded, Mr. Murray meets with contractors to go over their respective logistics execution strategies. Those conversations focus on safety constraints, loading strategies and determining how to sequence the different trade specialists throughout construction.
“The best way to describe the sequence, schedule and logistics of a tall vertical building is creating a ‘parade of trades,’” he says. “Each trade group relies on and expects preceding work to be completed on time and to the expected level to allow its work to be completed in a predictable and efficient manner.”
“[W]e are focused on the safety of personnel and the speed of moving them and materials.”
—Jerry Bianco, Lendlease, New York, New York, USA
And once construction is underway, Mr. Murray uses a project planning system to outline and communicate the actions different contractors need to complete to move the project forward. These plans are distributed during weekly meetings and daily huddles, he says. “By constantly communicating, we address any issues and can avoid rework and delays.”
“Whatever you can do to reduce the number of workers and materials on site will speed construction and reduce risks.”
—George Argryou, Hickory Group, Melbourne, Australia
Proactive logistical planning also helps project managers identify opportunities to innovate, says George Argryou, managing director of Hickory Group, an integrated construction company in Melbourne, Australia. An emphasis on transporting workers and materials as quickly as possible has led to next-gen advancements in construction tech, such as super-fast elevators with fiberglass cables that are stronger and lighter than steel. These systems require less power and can rise higher than steel cable designs. The industry has also seen precast construction innovations that have helped speed up the construction process.
For example, Hickory's building technology system integrates the core, shear walls, bathrooms and facade of a building into a single prefabricated structure built off-site at the same time as other on-site work. This approach slashes the number of tradespeople working on-site and reduces the number of truck deliveries and crane time. The result: faster, safer and higher-quality construction with no impact to the budget and no changes to the original design. Mr. Argryou estimates that a typical tower project with 900-square-meter (9,688-square-foot) floor plates would use about 60 workers on the core structure and facade, building one floor per week. With the prefabricated approach, his project team needs just 20 workers—and they can construct up to two floors a week.
“This prefab process reduces 60 percent of the labor on-site,” Mr. Argryou says. “Whatever you can do to reduce the number of workers and materials on-site will speed construction and reduce risks.”
FROM ALL ANGLES
Peter Weismantle, director of super-tall building technology, Adrian Smith + Gordon Gill Architects, Chicago, Illinois, USA, is one of the lead designers for both the Burj Khalifa in UAE and the Jeddah Tower in Saudi Arabia—and he applied many lessons learned from the first project to the second. Most notably, Burj Khalifa used a tapered design to make the building narrower and more resistant to wind as it rose. However, the design featured tiers that stepped back at each level, which were difficult and time-consuming to construct.
The disruption caused by the tiered design resulted in months of delay as the team changed out rigging systems and concrete formwork, Mr. Weismantle says. So for the Jeddah Tower, his team applied a design with a smooth incline that doesn't require the extra steel and concrete steps.
“On Jeddah Tower, the reinforced concrete structure is very simple, with a vertical triangular core, vertical bearing fin walls, vertical corridor shear walls, sloped but continuous end walls and flat slab floors,” he says. “We saved a lot of time in construction without affecting the design goals.”
“Simply extrapolating ground wind speed data is not adequate when you get above about 600 meters.”
—Brian Jack, Adrian Smith + Gordon Gill Architects, Chicago, Illinois, USA
The design team has also worked closely with the client, local authorities and contractor to find other opportunities to improve efficiency and safety, says Brian Jack, director and project manager on the Jeddah Tower project for Adrian Smith + Gordon Gill Architects, Chicago, Illinois, USA. For example, the tower has a cantilevered skydeck on the 167th floor that the contractor could use as a crane platform during construction.
“We conferred with the contractor to understand temporary superimposed construction loads, and our structural engineer provided supplemental analysis to confirm the skydeck could be used in this fashion,” Mr. Jack says. “This is an excellent example of the beneficial collaboration between the design team and the contractor on large and complex projects.”
As skyscrapers reach new heights, developers and project managers must also consider the impact of high winds, both on the design and the safety of construction crews.
“Safety is what drives innovation on these projects,” says Mr. Bianco.
In recent years, his team started using a climbing formwork—a type of concrete mold for vertical structures that rises with the building. The formwork covers three to four floors, protecting workers from high winds and deadly falls, and can be jumped up a floor in advance of the next level of construction.
“When we started using this, everyone said it would kill the schedule because it would take so long to move. But it actually improved productivity,” Mr. Bianco says. As a result, the site is safer and workers are more comfortable working on the edge of the floors, which means they can accommodate more workers and complete more tasks in the same space.
The Jeddah Tower design incorporates features to mitigate the impact of high winds on the structure. One of the big challenges for this project was that no one had studied actual wind conditions at such extreme heights, says Mr. Jack. “Simply extrapolating ground wind speed data is not adequate when you get above about 600 meters [1,969 feet].”
So the designers partnered with Rowan Williams Davies & Irwin, a Canadian wind engineering firm that used a wind tunnel, weather balloons and sophisticated computer models to predict the impact of wind loads on the structure up to 1,000 meters (3,281 feet).
“The resulting data helped us design with confidence,” Mr. Jack says. The tower's shape features a broad tripod base that tapers to the top of the spire—and helped create dedicated entries for the building's three primary functions: office, hotel and residential. “This basic geometry is very stable and behaves extremely well under design window loads,” he says.
“Being a project manager on a supertall building project can be extremely intense and a lot more technical than a traditional building.”
—Peter Savoy, Mace, Jeddah, Saudi Arabia
The project managers on-site are still researching solutions that will keep workers safe—and reduce weather-related delays—in high-wind conditions. The team receives wind forecasts at 100-meter (328- foot) intervals twice each day to chart weather patterns over the course of the year, says Peter Savoy, construction director for Mace, the global consultancy that is part of the joint venture managing the Jeddah Tower project, Jeddah, Saudi Arabia.
The data indicates that high winds could lead to 35 percent downtime on cranes and hoists during construction in certain zones—particularly from 300 meters (984 feet) to 750 meters (2,461 feet). This would have a huge impact on delivery. To reduce downtime, Mr. Savoy and his team have looked into making changes to how materials and objects are lifted to the top of the building. For instance, large prefabricated steel cages can act like a sail in windy conditions and soon become unsafe to lift. Lifting smaller bundles means his teams can keep the work face open and keep production going smoothly.
“Being a project manager on a super-tall building project can be extremely intense and a lot more technical than a traditional building,” he says. “But it is a fantastic experience, and I feel lucky to be part of this project and the immense challenges it brings.” PM
Sky's the Limit
The skyscraper projects aiming to break records around the world.
Height: 462 meters (1,516 feet)
Location: St. Petersburg, Russia
Budget: US$2.5 billion
Highlights: Commissioned by Russian natural gas company Gazprom, the Lakhta Center will be the tallest building in Russia and Europe when it's completed in 2018. In 2015, the project team set a Guinness World Record for the largest continuous concrete pour—19,624 cubic meters (693,000 cubic feet) over 49 hours—which helped keep the project on schedule.
SUZHOU ZHONGNAN CENTER
Height: 729 meters (2,392 feet)
Location: Suzhou, China
Budget: US$4.4 billion
Highlights: This mixed-use tower would be the first supertall building in Suzhou. The design of the 137-story building features a network of columns and outriggers attached to the concrete core to form a flexible frame that can stand up to high winds. Launched in 2014 and scheduled for completion by 2021, construction is on hold because of financial difficulties.
◀ SHANGHAI TOWER
Height: 632 meters (2,073 feet)
Location: Shanghai, China
Budget: US$2.4 billion
Highlights: China's tallest building and the third super-tall tower in Shanghai's skyline was completed last year. The building has been rated LEED Platinum, making it one of the greenest super-tall buildings in the world. Its many sustainable attributes include 200 rooftop wind turbines that generate 10 percent of the building's electricity, a rainwater capture system, wastewater recycling and 24 sky gardens. The twisting design helped to reduce the impact of wind and the amount of steel needed, saving an estimated US$58 million in material costs.
JEDDAH TOWER ▶
Height: 1 kilometer (3,281 feet)
Location: Jeddah, Saudi Arabia
Budget: US$1.2 billion
Highlights: Launched in 2013, the slender tower is expected to be the world's tallest by the time the project is slated to close in 2022. Each side of the triangle-shaped building will provide a dedicated entrance for its three primary functions: office, hotel and residential.
◀ SKY MILE TOWER
Height: 5,577 feet (1,700 meters)
Location: Tokyo, Japan
Budget: None yet reported
Highlights: If built, this proposed skyscraper would be nearly twice the height of the Burj Khalifa. The residential tower would feature incremental tapers and vertical slots in the structure to mitigate the impact of the wind. The design also incorporates an articulated facade that facilitates the harvest and storage of cloud water, which would lower the time and cost of pumping water from the ground. No construction date has been proposed.
BIG BEND SKYSCRAPER ▶
Height: 4,000 feet (1,219 meters) in overall length
Location: New York, New York, USA
Budget: None yet reported
Highlights: Designer Oiio Studio has a unique twist to create the world's longest building: Erect twin towers that are joined by a curved top. The concept would result in a single building that—at its peak—would be roughly 717 feet shorter than the Burj Khalifa. But total from end to end, it would qualify as the world's longest. There's no telling when—or if— the tower will be built.
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